Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $176.85   11.371%   $196.9596   $196.96   $196.95   $197.00  
  Purchase #2 $200.31   8.676%   $217.6889   $217.69   $217.70   $217.70  
  Purchase #3 $127.88   6.700%   $136.448   $136.45   $136.45   $136.40  
  Purchase #4 $195.78   9.664%   $214.7002   $214.70   $214.70   $214.70  
  Purchase #5 $9.69   9.312%   $10.5923   $10.59   $10.60   $10.60  
  Purchase #6 $12.28   6.526%   $13.0814   $13.08   $13.10   $13.10  
  Purchase #7 $230.35   6.719%   $245.8272   $245.83   $245.85   $245.80  
  7 purchase totals = $953.14       $1,035.2976   $1,035.30   $1,035.35   $1,035.30